ON THE EVIDENCE OF DETERMINISTIC CHAOS IN ECG - SURROGATE AND PREDICTABILITY ANALYSIS

The question whether the human cardiac system is chaotic or not has be en an open one. Recent results in chaos theory have shown that the usu al methods, such as saturation of correlation dimension D-2 Or the exi stence of positive Lyapunov exponent, alone do not provide sufficient evidence to confirm the presence of deterministic chaos in an experime ntal system. The results of surrogate data analysis together with the short-term prediction analysis can be used to check whether a given ti me series is consistent with the hypothesis of deterministic chaos. In this work nonlinear dynamical tools such as surrogate data analysis, short-term prediction, saturation of D-2 and positive Lyapunov exponen t have been applied to measured ECG data for several normal and pathol ogical cases. The pathology presently studied are PVC (Premature Ventr icular Contraction), VTA (Ventricular Tachy Arrhythmia), AV (Atrio-Ven tricular) block and VF (Ventricular Fibrillation). While these results do not prove that ECG time series is definitely chaotic, they are fou nd to be consistent with the hypothesis of chaotic dynamics. (C) 1998 American Institute of Physics.